Portable devices embodying miniature electrodes or microsensors for measuring analytes, e.g., pH, pO.sub.2, PC0.sub.2, in fluids such as blood are known and described, e.g., in U.S. Pat. No. 4,339,317 and U.S. Pat. No. 4,615,340. The '340 patent describes a hand-held sensor assembly comprising a reusable housing portion having sensor electrode means contained therein and a detachable, disposable blood sampler portion associated therewith. The '317 patent describes a disposable hypodermic syringe, the reusable piston of which has a plurality of microelectrodes disposed in its face.
The present invention provides a sensor assembly that is convenient to use and offers the advantage of being completely disposable after a single use. Also, since the sensor electrodes are calibrated immediately before use, accurate, error-free measurements are assured.